Petrologic and geochemic features of ore-containing substratum in hydrothermal gold deposits P. 2. Petrologic and geochemical concept of near-ore metasomatism

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Abstract

The relevance of the research is caused by the necessity to correct and elaborate on geological (metallogenical) component of the hydrothermal gold deposits formation theory within the framework of which the conflicting ideas about ore-formation geological making (energy and metalliferous fluids sources) go in four competing hypotheses eliminating one other. Therefore it is impossible to develop a complex of effective forecast-search mineralization criteria. The main aim of the study is to prove: 1) the belonging of epigenetic mineral associations at the ore-formation stage in near-ore alterating black shales series to metasomatic formations, contrary to the wide-spread ideas, and, as consequence, material-genetic similarity of apoblackshales zoning metasomatic columns (haloes) with those, formed in non-shale (crystalline) substratum; 2) external (non-rock) sources of gold and other metals, concentrated in deposits formed in black shales series. The methods used in the study. 1) Atom-absorption (sensitivity 1-10-8wt. % for gold, silver, 5-10-7wt. % for mercury), controlling neutron-stimulate, chemical-spectrum analysis for gold (sensitivity 1-10-8and 3-10-8 wt. % accordingly). 2) Calculations of statistical parameters of metal distribution and balance in near-ore expanse of deposits using two-level system of selections, to ensure reconstruction of chemical elements geological history and proper appraisal of donor potential of the rocks including black shales. The results. 1) Distribution of gold and accompanying metals in near-ore space is subject to metasomatic zoning - near-ore geochemical haloes always take up lesser volumes comparatively with the near-ore metasomatic ones. It is expressed in subclark contents (0,5⋯ 1,2 mg/t) and low distribution dispersion of gold, silver, mercury in various rocks, including black shales regionally metamorphosed on muscovite-biotite paragenesis level outside and in weak alteration subzone of frontal zone of near-ore metasomatic haloes, and in sequential increase of these parameters, as well as Au-Ag-relation and correlative connections between gold and silver from one mineral-petrochemical zone to another at intensification of near-ore metasomatic rocks alterations with achievement of maximum quantities in rear zone the more the higher metal contents in ores. 2) The Petrologic Geochemic concept (model) of the near-ore metasomatism in the mesothermal gold deposits is developed and described. It includes: a) the proofs of the article of ore-formation stage epigenetic mineral associations in near-ore alterating black shales series, contrary to metamorphogenous and poligenous ore-formation hypothesis, to metasomatic formations, formed in non-shales (crystalline) substratum; b) sinore origin of contrasting geochemic anomalies of metals (their beyong-clarc contents) in near-ore mesothermal gold deposits space, that is external (non-rock) of gold and other metals sources, concentrated in deposits formed in black shales series and crystalline substratum. The results obtained fit in well in the proofs system of the geologic genetic of discussing combinations of gold-ore deposits monotony, their belonging to mesothermal ones and formation in black shales series and non-shale substratum in composition of gold-productive antidromic fluid-ore-magmatic granite-diorite-dolerite complexes on late (basaltoid) stages of their functioning.

Original languageEnglish
Pages (from-to)6-19
Number of pages14
JournalBulletin of the Tomsk Polytechnic University, Geo Assets Engineering
Volume327
Issue number5
Publication statusPublished - 2016

Keywords

  • Black shales
  • Crystalline (non-shale) substratum
  • Geochemic haloes
  • Hydrothermal gold deposits
  • Near-ore (ore-containing) zoned metasomatic

ASJC Scopus subject areas

  • Economic Geology
  • Geotechnical Engineering and Engineering Geology
  • Fuel Technology
  • Management, Monitoring, Policy and Law
  • Waste Management and Disposal
  • Materials Science (miscellaneous)

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